Restructure changelog

CHANGES.md

@@ -3,14 +3,18 @@ Synapse 1.49.0 (2021-12-14)
 
 No significant changes since version 1.49.0rc1.
 
+
+Support for Ubuntu 21.04 ends next month on the 20th of January
+---------------------------------------------------------------
+
 For users of Ubuntu 21.04 (Hirsute Hippo), please be aware that [upstream support for this version of Ubuntu will end next month][Ubuntu2104EOL].
 We will stop producing packages for Ubuntu 21.04 after upstream support ends.
 
 [Ubuntu2104EOL]: https://lists.ubuntu.com/archives/ubuntu-announce/2021-December/000275.html
 
 
-Synapse 1.49.0rc1 (2021-12-07)
-==============================
+The wiki has been migrated to the documentation website
+-------------------------------------------------------
 
 We've decided to move the existing, somewhat stagnant pages from the GitHub wiki
 to the [documentation website](https://matrix-org.github.io/synapse/latest/).
@@ -27,6 +31,9 @@ requests](https://github.com/matrix-org/synapse/pulls). Please visit [#synapse-d
 if you need help with the process!
 
 
+Synapse 1.49.0rc1 (2021-12-07)
+==============================
+
 Features
 --------